1. Field of the Invention
The present invention relates to an electrophotographic imaging apparatus, and more particularly to a fuser oiling apparatus and the associated method involved with its use and operation.
2. Description of the Related Art
In the electrophotographic process commonly used in imaging apparatus such as laser printers, an electrostatic image is created upon a photosensitive member such as a roll or belt. Visible electroscopic marking particles, commonly referred to as toner, are applied to the electrostatic image on the photosensitive member. Thereafter, the toner is transferred to the desired media, which may include paper, transparency sheets or the like.
Until the toner is fixed by the application of heat, the toner image applied to the media is not permanent. During fixing, the toner is elevated in temperature sufficiently to cause constituents of the toner to become tacky, and flow into the pores or interstices between fibers of the media. Upon cooling, the toner again solidifies, causing the toner to adhere to the media. Pressure may be applied to enhance the flow of the toner, and thereby improve the subsequent bonding of the toner to the media.
An approach used commonly for thermally fixing an electroscopic toner image includes passing the media, with the toner image thereon, through a nip formed by opposed rolls, at least one of which is heated either internally or externally such that the roll surface is at an elevated temperature. The heated roll, referred to as a fuser roll, contacts the toner image, thereby heating the image within the nip. Under some operating conditions, the tackiness of the toner upon heating can cause the mediator adhere to the fuser roll and/or may cause a build up of toner on the fuser roll. By controlling the heat transfer to the toner, transfer of toner to the user roll can be minimized. In a duplex imaging apparatus, wherein both sides of the media may be printed, toner transfer or media sticking problems may be enhanced. Further, toner may be transferred to the backing roll of the fuser roll couple, and transferred thereafter elsewhere in the apparatus. The presence of wayward toner particles in the imaging apparatus can degrade the quality of the printed sheets.
Fuser of the type described above commonly employ an apparatus for applying a release fluid to the surface of the fuser roll. The release fluid creates a weak boundary between the heated roll and the toner, thereby substantially minimizing the offset of toner to the fuser roll, which occurs when the cohesive forces in the toner mass are less than the adhesive forces between the toner and the fuser roll. Silicone oils having inherent temperature resistance and release properties suitable for the application are commonly used as release fluids. Polydimethylsiloxane is a silicone oil that has been used for this purpose advantageously in the past.
Various methods and apparatuses have been used to supply oil to the fuser hot roll, including oil wicking systems, oil delivery rolls, and oil webs. Oil wicking systems include reservoir tanks of the desired release agent or oil, and a piece of fabric wick material having one end mounted in the reservoir and the other end spring biased against the hot roll. Oil from the reservoir is drawn through the fabric wick by capillary action, and is deposited against the roll surface. While a wicking system can be effective in supplying oil to the fuser roll, surface deposit of the oil on the roll can be inconsistent, and the replenishment or replacement of the oil and/or system can be difficult and messy.
A variety of oil delivery roll systems have been used in the past, and include a roll nipped against the hot fuser roll. The oil delivery roll may be either freely rotating against the fuser roll or driven against the roll through a gear train. Oil delivered to the surface of the oil delivery roll is deposited on the hot fuser roll as the rolls rotate against each other. Various structures have been used for providing oil to the surface of the oil delivery roll, including reservoirs at the center of the roll providing oil to the surface through small dispersal holes or via capillary action through the outer material. Felts or metering membranes may be used in the oil delivery roll to control the oil flow through the roll. Another style of such roll is referred to as a web wrapped roll, and includes high temperature paper or non-woven material saturated with oil, and wrapped around a metal core. In yet another type of oil delivery roll, the roll rotates in a vat or reservoir of release oil, picking up a coating of the oil or release agent, which is then, in turn applied to the fuser roll. It is also known to use a roll couple in applying the oil from the vat onto the fuser roll. A first pickup roll rotates in the oil contained in the vat and is nipped against an applicator roll. The applicator roll is nipped against the fuser roll. Oil picked up by the pickup roll is transferred to the applicator roll, and is subsequently transferred to the fuser roll. Doctor blades may be used to remove excess oil from the pick-up roll. Arrangements of this type can suffer from similar problems of resupply and cleanliness as oil wicking systems.
Oil web systems include a supply spool of web material, generally being a fabric of one or more layers saturated with the desired oil. A take-up spool is provided for receiving the used web. A web path, commonly including one or more guide rolls, extends from the supply spool to the take-up spool. A portion of the web path brings the web material into contact with the hot fuser roll, either by wrapping a portion of the web around the hot roll, or by utilizing a spring-biased idler roll to nip the web material against the hot roll. As the hot roll rotates against the web in contact therewith, oil is transferred from the web to the fuser roll. Periodically, a drive mechanism for the take-up spool activates, rotating the take-up spool and advancing web material from the supply spool to the take-up spool, thereby bringing a fresh section of web material into contact with the fuser roll.
Oil web systems can be used to deliver oil with good uniformity across the fuser roll surface. However, the texture of the oil web makes the web abrasive. As the fuser roll rotates against the oil web, the oil web can cause degradation of the fuser roll surface. Any surface irregularities on the fuser roll can lead to print quality reduction. Minimizing the abrasive quality of the web, while retaining the required properties for oil retention and subsequent oil transfer can be done only with costly materials, or with multi-layer webs difficult and expensive to manufacture, substantially increasing the cost for new or replacement oil web systems.
What is needed is an oil web system for an imaging apparatus fuser drum which retains the advantages of an oil web system, such as cleanliness, ease in replacement and consistency in performance; while eliminating the disadvantages in known oil web systems, such as the abrasive contact between the oil web and the fuser drum.
The present invention provides an imaging apparatus having an oil web system for applying release oil on the fuser roll, and an operating method for an oil web system, whereby the abrasive effect of the web against the fuser roll is eliminated.
In one form thereof, the present invention comprises an oil web system having an elongated web with fuser release agent impregnated therein, a supply spool for unused portions of the web, and a take-up spool for used portions of the web. An applicator roll has an outer surface in contact with the fuser roll. A transfer station transfers release agent from the web to the applicator roll.
In a second form thereof, the invention comprises an imaging apparatus, including a fuser having a hot roll, a backing roll and a fuser nip formed between the hot roll and the backing roll. An oil web system is provided, including an applicator roll disposed in contact with the hot roll, a material web having release fluid therein, a supply spool and a take-up spool for the web, and a transfer station operating with the web and the applicator roll to transfer release fluid from the web to the applicator roll, and a web advancement means for advancing the material web between the supply spool and the take-up spool.
In yet another form thereof, the invention comprises a method for applying release fluid onto the surface of a fuser roll, including providing a web of material having release fluid therein, a supply spool for unused portions of the web and a take-up spool for used portions of the web; providing an applicator roll disposed in contact with the fuser roll; transferring release fluid from the web to the applicator roll; and applying release fluid on to the fuser roll with the applicator roll.
An advantage of the present invention is the consistent application of release fluid on the fuser roll.
Another advantage of the present invention is reduced wear on the fuser roll.
Yet another advantage of the present invention is the elimination of the abrasive contact between the fuser roll and the oil web.
A further advantage of the present invention is increased expected operating life for the fuser roll.